This invention relates generally to filtering devices and more particularly to a dual filtering system which allows fluid flow to continue through the filter even after the primary filter element has become clogged.
In many of todays high temperature, high output engines such as found in ships, automobiles and, more particularly, aircraft it is essential that these engines produce a high output as efficiently as possible. In the area of aircraft engine design, the following are some of the major design, process and material details and component improvements that have been utilized to permit higher speeds and higher cylinder temperatures and pressure, and to reduce local hot spots for higher overall engine performance on a given fuel: (1) higher-strength and temperature resistant materials resulting from alloy improvement; (2) use of induction hardening, carburizing of nitriding steels for higher strength and long wear characteristics, particularly where rubbing occurs, such as on cylinder barrel walls, piston rings, crankshafts, piston pins, link pins, and gears; (3) use of shot peening or surface rolling on highly stressed parts to eliminate residual stresses and add light compressive stresses for maximum uniformity, particularly at stress concentrations such as valve springs, connecting rods, rocker arms, and welded areas; (4) surface coating for improved functioning, which included such items as steel-backed, silver-plated master rod bearings with lead-indium coating; flame plating of high temperature alloys on valve seat faces and insert seats; and silver, copper, or other coating, plating, or surface treatment to eliminate fretting, fretting erosion, or other action leading to fatigue cracks; (5) closer spacing and thinner fins or aluminum cylinder heads and steel barrels, with improved baffling for more uniform and better cylinder cooling; and (6) tapered piston rings for higher-temperature piston operation without ring sticking.
One area which has not been covered above and which is extremely essential in high speed engine design is the fluid filtering system. This system, for efficient operation, requires periodic and systematic cleaning or replacement of filtering elements to avoid eventual clogging of these elements. As they become clogged a gradual lessening of output pressure begins. To overcome this problem, in the past, these filtering elements had to be replaced at frequent intervals so as to avoid any engine inefficiency, or complete breakdown. Such a continual replacement of filters is not only expensive but also time consuming. In addition, if these filters are not changed at frequent intervals in time engine failure may easily occur.